Acura RSX, ILX and Honda EP3 Forum banner
1 - 20 of 107 Posts

· Not a Newb Member
Joined
·
1,101 Posts
Discussion Starter · #1 · (Edited)
I recently took a vehicle dynamics class. We needed to do a class project, so I (and two additional group members) chose to model the RSX suspension. I am attaching the final report so that everyone here can benefit from it. Note, I am posting this here in the autocross forum rather than the suspension forum because it is more relevant to those of us who track our cars or do autocross.

Basically, the car's suspension was measured so that the location of every suspension point was known in x, y, and z coordinates. Next, the suspension was modeled in Solidworks. From this point, lots of info can be measured/calculated.

Anywho, we looked at camber gain, both from suspension compression and from steering input. We also did roll center heights and bump steer. All of these were done for the front and rear. Additionally, aftermarket modifications were 'made' to the model and their effects on the above parameters analyzed. The modifications made were roll center adjusting ball joints, caster/camber plates that move the strut top inward 3/4" and rearward 3/4", raising the inner tie rod ends 1.25", and lowering the inboard side of the rear top link of the rear suspension 3/4".

DISCLAIMER: Every attempt was made to be as accurate as possible during this project. However, it is exceedingly difficult to measure the suspension perfectly. As such, I do not guarantee any values as being 100% exact. They should be pretty darn good though.
 

Attachments

· Here goes nothing
Joined
·
2,607 Posts
Your recommendation to maximize camber using bolts rather than plates is interesting. I theorized the same thing and had the shop max my Ingalls bolts out before touching the plates. In addition, it minimizes the toe impact since you're moving the strut, and therefore the steering arm, less.
 

· Registered
Joined
·
141 Posts
Thanks guys! This is probably some of the best information I have gotten from this board. As an off road racer, we are more concerned with tuning our suspension to go through things rather than around them! Not being an engineer, I have been kind of struggling with the principals of how our cars work. Discussions like these really help.
 

· Registered
Joined
·
176 Posts
Best thread I've come across on this site so far. But then again, I'm biased towards technical gems like this. This should be required reading for anybody who tracks/races an RSX.

Thanks for sharing!

Edit: Do you have any calculated info for motion ratios? I've found some values elsewhere on CRSX, but it would be interesting to see if your modelling produced similar results. Maybe some of the mods you analyzed affect the motion ratios; that would be handy to know.

And again: When you refer to the "nominal location" of the suspension, is that the OEM ride height or something lower? I'm just wondering what ride height actually corresponds to the zero compression reference on the plots.
 

· Not a Newb Member
Joined
·
1,101 Posts
Discussion Starter · #13 ·
Best thread I've come across on this site so far. But then again, I'm biased towards technical gems like this. This should be required reading for anybody who tracks/races an RSX.

Thanks for sharing!

Edit: Do you have any calculated info for motion ratios? I've found some values elsewhere on CRSX, but it would be interesting to see if your modelling produced similar results. Maybe some of the mods you analyzed affect the motion ratios; that would be handy to know.

And again: When you refer to the "nominal location" of the suspension, is that the OEM ride height or something lower? I'm just wondering what ride height actually corresponds to the zero compression reference on the plots.
Thanks!

Actually, I have been meaning to calculate the motion ratios as a function of suspension compression (they likely change a little bit as the wheel moves up). I'll report back after I do.

The nominal location refers to the stock/oem ride height, as the car sits normally (aka, zero on all the graphs).
 

· Billy Ball is in effect
Joined
·
6,412 Posts
From a fellow engineer, props! Very well done.
 

· Registered
Joined
·
9,621 Posts
wait wait wait...

Why does shimming the rear upper link raise roll center?

Did I draw this wrong? Seems like roll center gets lowered.


Also, how does the use of camber plates improve camber gain under compression? Just less compliance?

Lol the results of camber plates + RCA + raised steering rack bracket is alarming. Although I'm going to keep my current setup. Explains why I like the feeling of lots of toe out and the lack of traction is I run 0 toe as opposed to toe out.
 

· Not a Newb Member
Joined
·
1,101 Posts
Discussion Starter · #16 ·
wait wait wait...

Why does shimming the rear upper link raise roll center?

Did I draw this wrong? Seems like roll center gets lowered.


Also, how does the use of camber plates improve camber gain under compression? Just less compliance?

Lol the results of camber plates + RCA + raised steering rack bracket is alarming. Although I'm going to keep my current setup. Explains why I like the feeling of lots of toe out and the lack of traction is I run 0 toe as opposed to toe out.
I was waiting until you noticed that:) It has troubled me too. Unfortunately, I don't have a concrete answer for you. I do know that the rear suspension only vaguely resembles a double wishbone design. The lower control arm 'hinge' is at a huge angle, rather than parallel to the centerline of the car. Plus, the upright/knuckle is attached to the lower control arm at a crazy angle itself. All this 3D nature must be having an effect...I don't know why else the roll center would raise. It doesn't seem intuitive, but I trust the model and calculations.:dontknow:
 

· Registered
Joined
·
9,621 Posts
I was waiting until you noticed that:) It has troubled me too. Unfortunately, I don't have a concrete answer for you. I do know that the rear suspension only vaguely resembles a double wishbone design. The lower control arm 'hinge' is at a huge angle, rather than parallel to the centerline of the car. Plus, the upright/knuckle is attached to the lower control arm at a crazy angle itself. All this 3D nature must be having an effect...I don't know why else the roll center would raise. It doesn't seem intuitive, but I trust the model and calculations.:dontknow:
Haha I trust it too, I'd just like to understand it better.

Oh well, I'm glad I didn't shim my upper arm yet. I think the rear has enough camber gain (based off the amount of static camber I run).

But maybe... maybe I can lower my rear static camber by running the shims and help make my rear brakes work harder to slow the car down which might make me faster? :dontknow:
 

· Here goes nothing
Joined
·
2,607 Posts
I'm curious though... everything I've read about this chassis for the last 9 years, as well as generally understood behavior of macstrut suspensions, suggests camber loss with compression. Unless I'm reading this wrong, you're suggesting the RSX gains negative camber w/ compression? That's an entirely new assertion. It makes me weary of the model.

I'm not challenging your intent or qualifications, but as a software engineer I know everything, especially the first time around, has at least a few bugs ;)
 
1 - 20 of 107 Posts
Top